Today I was trying to make a backup of my Windows PCs to the MBWE, using the built-in backup software. But, guess what; that didn't work. Everytime I selected the share [which had the correct permissions], it wrote some .TMP files, and a {..GUID-Style..} directory, and immediatelly dying with 0x800700b7 error.

After looking on several websites, I've found the silver bullet: Just create a user "Everyone" on your MBWE, set a password, create a share on your MBWE, grant access to the "Everyone" user on that share and when Windows Backup asks for the username & password for the share, type Everyone and the password.